Synchrotech Replacement K Series Synchro Set for Honda/Acura

Synchrotech K-Series Synchro Set - Carbon or Brass

If your K-series grinds going into gear, the synchros are what's worn. This is the set that replaces them, and nothing else. No springs, no bearings, no sleeves, just the synchro rings in either brass or Synchrotech's carbon composite. If you've had the transmission open, inspected everything, and found the synchros are the problem, this is the part rather than a full kit you don't need.

Which Part Do You Actually Need?

Three parts, three different symptoms. Match yours before you spend money.

That first one is what brings people here. When a synchro's friction surface wears down, it can't drag the gear to matching speed fast enough before the sleeve arrives, so the teeth clash instead of meshing. That's the grind, and it's usually worse on downshifts than upshifts.

Finding wear in more than one of these? The master rebuild kit covers everything at once and works out cheaper than buying the pieces separately.

Synchros Only, Nothing Else

Worth being clear, since we sell a few things that look similar.

This is synchros alone. No springs, bearings, seals, or sleeves. That makes it right when you've got the transmission open, you've inspected everything, and the synchros are genuinely the only thing past spec.

If your springs are tired too, and after this many years they usually are, look at the bearing and seal kit or the master kit instead. Springs are cheap and they directly affect how well a synchro engages, so reusing old ones behind new synchros is a common way to end up disappointed.

Carbon Or Brass?

Both fix a grinding transmission. They suit different cars.

Brass is the OEM-style material and the right pick for most street cars. It restores factory shift feel, it's proven over decades, and it costs less. Refreshing a daily driver, start here.

Carbon is Synchrotech's Pro Series, and it's genuinely different from OEM brass or the spray-coated and woven-fabric carbon synchros out there. These use a full carbon composite lining built on carbon-carbon technology originally developed for aerospace, and the material acts as a braking element during engagement. It stops the gear faster, which means less grind on high-rpm shifts and less wear on your sleeves and engagement teeth. If you shift hard, run track days, drag race, or make real power, this is the one.

One honest note: carbon shifts better, but don't buy it expecting dramatically longer life than brass. You're paying for how it engages.

Pick Your Set Carefully

Two things determine which set you need: how many gears you're covering, and what synchro design your transmission uses. Get both right.

Two Things That Catch People Out

The 5th and 6th gear split. SYN118 and SYN117 both cover gears 1 through 6, and they are not interchangeable. The difference is entirely in 5th and 6th: one uses a dual cone 3-piece design, the other a single cone 1-piece. Look at what's actually in your transmission rather than going by the car, because both sets list the same models.

Only need the low gears? SYN119 covers 1 through 4 on 6-speed transmissions. If your grinding is isolated to the gears you actually use hard and 5th and 6th are still fine, that's the more sensible buy. First through third take the most abuse on almost every car.

If you're not certain which design you've got, check the transmission code on the case and inspect the synchros with the case open. Getting this wrong means parts that won't work in a job you don't want to do twice.

Check Your Hubs And Sleeves While You're In There

The most important advice on this page. Synchros work against your hubs and sleeves, and if those surfaces are worn, new synchros of any material won't fix your shifting. New carbon on a chewed-up hub is no better than new brass on a chewed-up hub.

So inspect before you close it up. Look at the engagement teeth, the sleeves, and the hubs. Sharp and clean means this set will transform the shift. Rounded off means you need those parts too, and finding out now is far better than after everything's back together.

Worth Doing Once

Getting into a K-series transmission is most of the work on this job, whether you're paying a shop or spending your own weekend. The parts are the cheaper half by a wide margin. So while it's open, inspect everything and replace what's genuinely past spec rather than what you assumed was bad. That's how you close it up once and get the shift you were after.

Who Should Run This Set

This is for the builder who's already in the transmission, has inspected it properly, and knows the synchros are the problem. You're buying exactly what you need without paying for parts that are still good. If you haven't opened it up yet, or you're finding wear in several places, the master kit is the better value. Pick brass or carbon based on how you drive, match your set carefully, and get your shifts back.

Fits: Honda and Acura K-series transmissions, see the table above. Materials: brass (OEM-style) or Synchrotech Pro Series carbon composite. Includes: synchros only. No springs, bearings, seals, or sleeves. Part numbers: SYN119 (1-4, 6-speed), SYN118 (1-6, dual cone 5/6), SYN117 (1-6, single cone 5/6), SYN116 (1-5, 5-speed), SYN114 (CR-V / Element / Accord APG6). Important: confirm both your gear coverage and your synchro design before ordering.